Safety device for electric circuits.



' with the amperage.

'UNITED STATES PATENT oEEIoE.

oLoE rE'rEnsoN, or DE Katia, AND HARRY c. SMITH, or GENEVA. ILLINOIS.

SAFETY DEVICE FOR ELECTRIC CIRCUITS.

Specification of Letters Patent. Patentd Nov. 10, 1914.

Application lfiled May 16, 1914i.v Serial N0. 838,929.

To all whom it may conce Be it known that we, L'iior PETERSON and HARRY C., ASMrrri, citizens of the United States, residing, respectively, at De Kalb in the county of Dekalb, State of Illinois, and Genera, in the county of Kane.. State of lllinois, have'jointly invented certain new and useful linproveiiients;in Safety Devices for Electric Circuits, of which the following is specification.

Our invention relates in general to safety devices for electric circuits and ,has for a principal `objectthe provision. of a safety device for a circuit carrying a relatively low voltage. Y

Our invention has particular refer-ence to safety or blow-out devices for use in electric house-lighting circuits where it is extremelyl desirable to prevent a. current of materially .E higher voltage than that'for which the cir-v cuit isv adapted t-o be introduced into the circuit. These circuits'carry usually a current of il() or 220 volts which is'. delivered to them through transformers ffroin a service line or circuit carrying current of `much higher potential, 'often 2200 or '2500 volts. lf lightning strikes the servi-ce line the insulation in the transformer separating the primary and secondary circuits. often breaks down and .lets the wires composing. these two windings come in contact'. When this occurs or when a high tension line wire falls across or comes in contact with a side of a house circuit, the high tension current ofthe service circuit oi other line wire as the case may be is transmitted directly to the house lighting circuit. This usually produces no immediate efe'ct as the devices the house lighting circuit are only concerned Should, however, an individual touch a lighting fixture whic'li'is not insulated for such high potential he is likely to forni a ground connection and be killed as a result. This high -potential in the house circuit often causes, moreover, the

breaking down of the. insulation of the" house. circuit and the consequent grounding through pipes or other conductors which results in sufficient sparking to set the house on nre. i

It is a principii object'of this invention t0 prevent a current of materially. higher voltage than that intended from entering the house circuit or any other circuit in connection with which :the device embodying our invention is provided,

provided inf o i l i i .A further .object of the invention is to .provide a safety device-of the character described of simple, economical an'd durable construction which may be easily installed. A. Apreferred forni of the invention is to be4 seen in the drawing/accompanying this application of which- 'Figure lis a' plan view, and Fig. 2 -is a vside elevation partly in section. Referring to the drawing l designates a- 'basc'of suitable insulating material. Upon this base, are mounted uprights 2,2` to which are pivotally connected-the knifeblades 3,. '3 which in turn may engage the clips,A 4;, 4

suitably mounted upon the base. A cross bar -5 and handle 6 of insulating material -are fpiovided as is usual iii knife-blade switches. `buitably mounted on the-basel and in electric connection with uprights '7 are clips 7, T which in connection with siini lar clips 8, 8 are adapted to hold fuses ofl standard type. The clips 8, S have the usual lugs 9, 9 to which wires may he soldered or otherwise attached. Mounted on the base 1' is a coiled spring l0 having an extended arm 1l which passes beneath the insulating cross bar so that when the switch is closed the .spring is placed under tension. Y The spring is made sufficiently strong to throw the knife blades 34 outof contact with the clips 4 when the spring is released.` Upon the base l is mounted an upright l2 upon which is'p-ivotally mounted alatch 13 which engages the spi-ing arin 11 when the switch is closed and restrainsit from displacing the knife blades.- l

To oneof the upriglits 2 is attached a wire 14 'which is' connected .with an upright 15 suitably mounted on base 1.- To

this upright andin electrical connection therewith av fusible wire 1G is attached. The fusible -wire 16 is attached at its other. exf trennt-y tothe linger ll' whichfornispart'of the -latcli- 13. The fusible wire 1'6 passes over a4 standard 1S which 'acts as a terminal for a ground wire', the usual lug 21 being provided for. connecting the` Wire, Upon thestandard vlS- and resting on the surface thereof beneath the fnsible'wirc 1li is a sheet of mica or'siniilar insulating materialv in the y center of which. is a small slit or opening 19;

The fusible wire is arranged to pass directly over this opening in such a manner thatl cuit it will ,deve-lop, an arc between the fusiblerwire 16 and thefstandard 19. thereby fusing the Wire.- The wire areY connected in the usual manner to the lugs20, a-nd a ground wire is connected'to the lug 21, as previously explained.V l f f The operation' of `our device is as follows: The switch being vclosed and the spring arm 11 held from acting'upon the' s amelby the latch 13, the low tension current ifo,- v from any source it willpass throughthe Vwill pass through' the circuit'. Should a high tension current leak into'- the circuit ground circuit 'wire' 14, upright 15 and fu-g sible wire 16, and overcoming the resistance v i of the air gap between the fusible'wire and the standard 18 it will cause'a spark-to form whichwill fuse the wire 16, 'thereby releas` 'final conditions exist'in the circuit.

ing'the' latch 13 and the lspring armf11 which willat onceopen the switch, breaking `the circuit and indicatingthat lthe abnor? fj The whole devicefis simple, eiiicient and" durable and `may be readily incorporated an ordinary yl`circuit, `it being necessary,

only to securethefbase -1.to al suitable sup? portgand connect'the wires in the' ordinary A manner. A wire should connect lthe ter- -minal'18 with a suitable ground. The de; vice'may be cheaply constructed as its parts maybe purchased at vany electrical supply house and easily assembled. It will be vobvious, moreoveigthat changes may be madeA =in the form, construction .and arrangement l-large-` volume goficurrentat a relatively low tension, means tendingA toi force said device to open position, means normally' restraining saidfirst-mentioned means, and anauxiliary groundedy circuit connected tol said.

- circuit includingI spaced conductors adapted to prevent'the passage of 'lowtension currents, oneof 'said' conductors being 'fusible and attached at one lend to said restraining means v2. In a safety device'for an electric vcircuit, the combination ofa circuit closing device in said circuit adapted to carry a large volume `of.'current at a relatively lov7 ten- "sioni, a spring Itendinglto force said device 'to 'open' position, means normally restraining said spring, andan 'auxiliary grounded `circuit connected-to said circuit .including spaced conductors'adapted to prevent the f passage oflow tension currents, one of said conductors being fusible at temperatures resulting from electric Isparks andjattached at one endto saidrestraining means.

In a safety vdevice for an electric cir-` cuit, the combination of a circuit closing de-` ".vicejnsaid circuit, meansI normally tending to force -said device to open position,

an auxiliary circuit comprising a fusible n means connected with thef'other end of the saidl fusible wire for, restraining. the firstmcntioned means.- v

Ll. In a-safetyA device for an electric circuit, the combination of a circuit-closing device inlsai'd circuit, a spring normally tending to force said device to open position, an auxiliary circuit comprising a fusible wire connected at on'e'end-with the said circuit, and ai lgrounded terminal Ain close relation .to said fusiblefwire, mea s for spacing said wire andterminal, whereby the passage of low tension currents is prevented, vand a latch connected with the other end ofthe said fusible wire for restraining the said spring. i

5.' In a safety device for an electric circuit, the combination of a circuitlosing device in said circuit adapted to carry a large volume of. current at a relatively low tenone of said conductors being fusible at tem- 100 peratures resulting from electric sparks and v attached at one end to said latch.

` i 4 oLor PETERSON.

HARRY C. -SMITI-I.

IVitnesses:

l OSCAR NELSON,

E. L. COLE.

A sion, a spring tending to force said device to 

